Colgate Total, one of Australia's most popular toothpastes, has come under international scrutiny over health concerns connected with one of its active ingredients, triclosan.

The toothpaste contains 0.3 per cent of the ingredient, the maximum level before it must be declared a poison by the Australian department of health's national industrial chemicals notification and assessment scheme.

The threshold for poison warnings was raised from 0.2 per cent after submissions claimed that it would have widespread commercial implications for a variety of industries.

Studies have shown links between triclosan and disrupted hormonal development, a reduction in bacterial resistance and an increase in allergies.

Australian experts have defended the product, the only toothpaste on the Australian market that contains triclosan.

They say the chemical has been proven to fight gingivitis, gum bleeding and inflammation.

"Untreated gum diseases have a massive effect," said Laurie Walsh, a professor of dental science at the University of Queensland.

"You have to balance the potential of harm against a known good."

But controversy over the chemical has existed for some time. Apart from the toothpaste, it is found in kitchenware, sanitation and toys.

In 2010 the European Union banned triclosan in all products that come into contact with food, but still allowed for it to be present in toothpastes up to a maximum of 0.3 per cent.

Then in December 2013 triclosan came under review by the US Federal drug administration (FDA) over its use in anti-bacterial hand soap, toys and cutting boards, amid concerns it could limit bacterial resistance and hormonal development.

"The big issue in handwash has been around spreading it on a wide area and absorbing it," said Professor Walsh.

"When you are brushing your teeth you are putting it in a very specific area for a very short amount of time."

At the same time, another US drug authority, the EPA, launched an investigation into the use of triclosan following "a rapidly developing scientific database".

The EPA is currently examining the impact of triclosan on thyroid hormones and estrogen levels, following studies that revealed disrupted development in animals.

Professor Walsh refutes the claims.

"There have been no concerns raised on our side that we have seen on patients," said Professor Walsh. "An animal study is an animal study, the evidence does not translate to humans."

There have also been concerns over links between triclosan use and sensitivity to allergens in patients.

The toothpaste, a staple of Colgate's 44.8 per cent share of the global market, has suffered significant consumer backlash since Bloomberg revealed in August that 35 pages of the original FDA approval process in 1997 were hidden from public view.

In August, the FDA admitted that the pages were not disclosed as the research into the safety of the product was conducted by Colgate.

Then, a former conmissioner of the FDA criticised the authority for withholding the information when there were concerns surrounding the potential cancer-causing properties of triclosan.

"Only confidential commercial information is redacted from public documents," the former commissioner, David Kessler, told Bloomberg.

"The real question is did Colgate do a good job?" Mr Kessler said.

An Australian study by academics at the University of Queensland found that over the course of four years, triclosan toothpaste had no ill-effect on the hormonal function of humans.